Study: Protecting old-growth can stave off global warming

If global warming occurs in the coming years as many scientists predict, the stands of big mature trees on local public forestlands could help save our bacon.

By Paul Fattig

If global warming occurs in the coming years as many scientists predict, the stands of big mature trees on local public forestlands could help save our bacon.

That's the upshot of a recently released peer-reviewed study of the Klamath-Siskiyou region in southwest Oregon and northwestern California by a University of Central Florida scientist and the Ashland-based Geos Institute.

"Climate change, combined with habitat loss and fragmentation, is the greatest threat we face to nature," said Reed Noss, one of the authors of the study and a professor of conservation biology at the University of Central Florida.

"This study shows that land managers can reduce impacts of climate change by protecting older forests in a region whose biological diversity has been recognized globally as among the top 10 coniferous forests on Earth," he added.

Published in the January edition of the science publication The Natural Areas Journal, the study, "Climate Change Refugia for Biodiversity in the Klamath-Siskiyou Ecoregion," concludes that mature and old-growth trees in the region help stave off rising temperatures near the ground, prevent the rapid loss of the mountain snowpack, retain cool stream temperatures and reduce the loss of fog in the coastal forests.

The study was led by forest ecologist Dominick DellaSala, chief scientist and president of the nonprofit institute, whose missions is to help people prepare for climate change and reduce its impact.

"For millennia our region's mature and old-growth forests have been a wellspring for nature," DellaSala said. "They now hold the keys to sustaining the very ecosystem benefits we will increasingly depend on for freshwater, clean air and viable fish and wildlife populations as global climate disruptions increasingly impact our area."

Mature tree stands, with their closed canopies and moist environments, are predicted to remain cooler for longer periods of time, providing a refuge for species that depend on cooler conditions, he noted.

"It's common sense — a lot of science is common sense," DellaSala said. "They act like a natural outdoor air conditioner as the planet heats up."

According to the study, regional average annual temperatures will increase from 1 to 3 degrees Fahrenheit by around 2040 and 4 to 8 degrees Fahrenheit by around 2080. It also predicts that average summer temperatures will increase from 7 to 15 degrees Fahrenheit by 2080.

That would result in less snow at lower elevations and a decrease in the average winter snowpack vital to spring runoff and stream flows, the study concluded. The climate change would also mean significant reductions in fog along the coast, posing risks to coastal redwoods, it noted.

In particular, forests on north-facing slopes and canyon bottoms, lower and mid-elevations and coastal mountains will help provide for cooler, moister conditions as the rest of the region heats up, the study said.

Researchers used computer mapping and databases on regional climate and wildlife distributions to determine which areas are likely to remain cooler if regional temperatures rise. The study includes a list of sites on Bureau of Land Management and national forestlands in southwestern Oregon and northwestern California where the scientists believe old trees should be retained because of potential climate change.